From: Jan Beulich <jbeulich@suse.com>
Date: Wed, 23 Mar 2016 10:05:23 +0000 (+0100)
Subject: x86/domctl: don't waste domain CPUID slots for all zero data
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~1509
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=0fa4c7f25dd0756fcc96de0824deb7763a7fa739;p=xen.git

x86/domctl: don't waste domain CPUID slots for all zero data

domain_cpuid() returns all zeroes anyway when not finding a match, so
there's no need to explicitly store such a set of values.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
---

diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index b34a295836..b7c7f424c4 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -714,7 +714,7 @@ long arch_do_domctl(
 
     case XEN_DOMCTL_set_cpuid:
     {
-        xen_domctl_cpuid_t *ctl = &domctl->u.cpuid;
+        const xen_domctl_cpuid_t *ctl = &domctl->u.cpuid;
         cpuid_input_t *cpuid, *unused = NULL;
 
         if ( d == currd ) /* no domain_pause() */
@@ -742,7 +742,12 @@ long arch_do_domctl(
 
         domain_pause(d);
 
-        if ( i < MAX_CPUID_INPUT )
+        if ( !(ctl->eax | ctl->ebx | ctl->ecx | ctl->edx) )
+        {
+            if ( i < MAX_CPUID_INPUT )
+                cpuid->input[0] = XEN_CPUID_INPUT_UNUSED;
+        }
+        else if ( i < MAX_CPUID_INPUT )
             *cpuid = *ctl;
         else if ( unused )
             *unused = *ctl;